I would go the gateway.
Though it is very small difference - IMO the AMD will run hotter, so your fan will be blaring away.
Plus the battery life is a bit better for the Gateway - probably because of the i5 architechture which has turboboost (the cpu will run at low speeds when needed, but with boost when needed) whereas the AMD will run at 'full' speed most of the time unless idling. This will impact on temperatures as well.
bumping to 500GB hdd is a bonus.
The other two have a dedicated number pad though - good for gaming sometimes.